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Fabrication of Polydiacetylene Liposome Chemosensor with Enhanced Fluorescent Self-Amplification and Its Application for Selective Detection of Cationic Surfactants Dong-En Wang, Lei Zhao, Mao-Sen Yuan, Shu-Wei Chen, Tianbao Li, and Jinyi Wang* Colleges of Science and Veterinary medicine, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China S Supporting Information *
ABSTRACT: Polydiacetylene (PDA) materials have been adopted as one of the powerful conjugated polymers for sensing applications due to their unique optical properties. In this paper, we present a new PDA liposome-based sensor system with enhanced fluorescent self-amplification by tuning a fluorophore fluorescence emission. In this system, a 1,8-naphthalimide derivative employed as a highly fluorescent fluorophore was incorporated into a PDA supermolecule. During the formation of blue PDA liposomes, the fluorescence emission of the fluorophore can be directly quenched, while thermal-induced phase transition of PDA liposomes from blue to red can readily restore this fluorescence emission. These phenomena could be ascribed to the tunable Förster energy transfer between the excited fluorophore and PDA conjugated framework. To demonstrate the sensing performance of this newly prepared PDA liposome-based sensor, the sensor with fluorescent self-amplification was successfully applied for the detection of cationic surfactants (CS). The results show that the PDA liposomes displayed a distinct color change and fluorescence restoration in the presence of cationic surfactant species, and allowed detection of cationic surfactants with high sensitivity and selectivity. The limit of detection for target CS, such as cetyltrimethylammonium bromide (CTAB), can reach as low as 184 nM. Compared to the traditional methods based on colorimetric PDA liposomes, this newly fabricated PDA sensor system was superior for sensitivity. Thus, our findings offer an avenue for the design and development of new types of PDA sensors with enhanced sensitivity. KEYWORDS: polydiacetylene liposome, self-amplification, sensors, energy transfer, fluorophore
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INTRODUCTION
great capability in the development of various chemical and biological sensors.19−27 In a typical design of a PDA sensor, a special receptor is rationally incorporated into PDA monomers or lipids. When the target molecule is introduced, the specific interactions of the receptor with the target analyte could cause the conformational change of the conjugated backbone to produce the dual signal change. Despite the successful development of PDA-based sensors for many chemical and biological analytes, there are still a few limitations for PDA-based sensors. For example, the sensitivity of PDA systems based on colorimetric detection in aqueous
There is considerable interest in the development of chemical and biological sensors based on conjugated polydiacetylene (PDA) due to the unique optical properties of PDA.1−3 The diacetylene monomer of PDA emerged usually as an amphiphilic substance can be facilely fabricated into films,4,5 nanowires,6−8 and liposomes.9,10 Under the irradiation of UV light, blue-colored PDA could be formed in situ through the rapid 1,4-addition reaction of well-ordered diacetylenes. When PDA is exposed to external stimuli, such as temperature,11−13 mechanical stress,14,15 and ligand−receptor interaction,16,17 colorimetric change of PDA from blue to red accompanied by fluorescence enhancement occurs, which is ascribed to the distortion of the ene-yne conjugated backbone caused by the external stimuli.18 This feature endows PDA materials with © XXXX American Chemical Society
Received: August 26, 2016 Accepted: September 29, 2016
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DOI: 10.1021/acsami.6b10794 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces
Scheme 1. Self-Assembly of PCDA-NG (or PCDA-EA-NG) and PCDA to Form Liposomes, and the Schematic Illustration of the Polymerization-Induced Fluorescence “Turn-Off” and Stimuli-Induced Fluorescence “Turn-On” Mechanism
fluorescence state of PDA liposomes, the fluorophore can harvest the energy and transfer it to the emission of red PDA liposomes, resulting in the amplification of PDA fluorescence signal. Although this process can increase the Stokes shift by moving the excitation light of PDA to a short wavelength (
